1. Field of the Invention
The present invention relates to a technology for discriminating conveyance propriety of a sheet used in an image forming apparatus when a clogging (hereinafter referred to as “jam”) of the sheet occurs.
2. Description of the Related Art
In an image forming apparatus, a jam of a sheet may occur due to a slip of conveying rollers or the like. In such a case, the sheet is to be removed manually, with the result that an excessive workload is imposed on a user. Further, even if the sheet is manually removed by the user, the jam may occur again due to a remaining piece of paper or the like. Therefore, there is proposed an image forming apparatus having an automatic sheet discharging function for discharging, at an occurrence of a jam, the sheet of which the jam has occurred automatically out of the image forming apparatus. Such an image forming apparatus is useful from the viewpoint of lightening the workload on the user. However, it may be impossible to perform automatic sheet discharging depending on a pattern of the jam of the sheet that has occurred. For that reason, it is necessary to determine in advance whether or not to perform the automatic sheet discharging.
Therefore, in the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2010-276930, based on a position on a conveying path of a sheet and a type of jam such as a delay jam or a retention jam, it is determined whether or not to perform automatic sheet discharging. Further, in order to grasp whether or not the subsequent sheet has bumped into the sheet of which the jam has occurred, the position of the subsequent sheet is verified by using a sensor.
In the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-154744, by dividing a conveying path provided with a flapper for a sheet into three segments, it is determined whether or not to perform automatic sheet discharging. Specifically, the conveying path is divided into a first segment in which the sheet of which a jam has occurred is located positively before the flapper, a second segment in which the sheet has already passed through the flapper positively, and a third segment in which the sheet is passing through the flapper. Then, based on which segment the sheet of which the jam has occurred remains in when the jam occurs, it is determined whether or not to perform the automatic sheet discharging.
However, in the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2010-276930, when the subsequent sheet is detected by the sensor, it is determined that the automatic sheet discharging cannot be performed regardless of presence/absence of buckling thereof. In other words, an occurrence of the buckling cannot be detected, and hence the sheet that can originally be subjected to the automatic sheet discharging may fail to be automatically delivered. Further, similarly in the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-154744, the position of the sheet can be detected at the occurrence of the jam, while the presence/absence of the buckling cannot be detected, and hence the sheet that can originally be subjected to the automatic sheet discharging may fail to be automatically discharged.
Therefore, present invention provides means to grasp a state of a sheet including presence/absence of buckling at an occurrence of a jam and determine more appropriately whether or not to perform automatic sheet discharging. The present invention also provides means to increase the frequency of executing the automatic sheet discharging, to thereby further lighten the load on the user at the occurrence of the jam.